I. Field of the Invention
The invention relates to a retro-reflective marker for mounting to roads, and more particularly, to a snowplowable marker having ramps to protect a reflector.
II. Description of the Prior Art
In many regions, plastic retro-reflective road markers are mounted to the road surface to delineate the lanes. Retro-reflective markers mounted directly into the road surface are frequently removed or damaged by the passing of snowplow blades in regions where snowplows are used to clear the roads. In these regions, it has become a practice to mount the plastic marker with a retro-reflective lens in a metal casting base member such as disclosed in U.S. Pat. No. 4,147,447. The base member includes a pair of spaced apart keel portions which are mounted in grooves formed in the pavement. The upper portion of the keels define a pair of ramps for deflecting the snowplow blades from a plastic reflector. The reflector is mounted between the longitudinal ramps in a center portion of the casting extending between the keels. However, the reflector lenses of previously known markers have been damaged when the blade of a snowplow is angled sharply. When the blade is sharply angled, such as 45.degree. to the axis of the road, the corner of the blade can pass between the ramps to damage the marker before it is deflected by the ramps.
Additionally, it has been difficult to accurately position prior art castings with respect to the road surface. If the casting is placed too low, the lens is obscured and there is insufficient light reflected from the lens to delineate the lane. If the casting extends too far above the road surface it becomes a hazard for vehicles passing over it and is more likely to be dislodged by the blades of the snowplow.
Accordingly, it is desirable to have a casting for a snowplowable road marker which properly provides full protection for the marker from damage by the snowplow blade and can be accurately positioned with respect to the road surface.